In the past, prime movers, such as dynamoelectric machines or electric motors for instance, were provided with a stationary assembly having a rotatable assembly disposed in magnetic coupling relation therewith. The rotatable assembly included a shaft having a pair of opposite end portions which were rotatably supported or otherwise suitably journaled in the stationary assembly. A rotor was mounted to the shaft, and a pair of thrust devices were disposed on the shaft with respect to the opposite end portions thereof for bearing engagement with a pair of confronting thrust surfaces provided therefor on the stationary assembly. Of course, the axial movement or end play of the rotatable assembly with respect to the stationary assembly was predetermined by the axial distance between the thrust devices on the shaft and their associated thrust surfaces on the stationary assembly, respectively.
In these past rotatable assemblies, the shaft thereof was mounted in displacement preventing engagement with the rotor by several well known manufacturing processes. One of these processes was to provide a conventional knurl, such as for instance a diamond knurl or axial knurl, at a preselected location on the shaft and then press-fit the bore of the rotor on such conventional knurl into displacement preventing engagement therewith. Another of these past manufacturing processes involved heating the core to effect its expansion and the expansion of the bore thereof, locating the expanded bore in the preselected location thereof about the shaft, and cooling the rotor to effect thermal shrinking of the rotor bore into displacement preventing engagement about the shaft. Of course, one of the disadvantageous or undesirable features of such past thermal shrinking process is believed to be that it was impossible to remove the rotor from the shaft without destroying the shaft and/or the rotor.
In the past, the thrust devices, such as thrust collars or the like for instance, were also mounted to the shaft generally in the same manner as discussed above with respect to rotors. For instance, an annular thrust collar was heated and thermally shrunk into displacement preventing engagement about the shaft at a preselected location thereon; however, at least one of the disadvantageous or undesirable features with respect to such thermal shrinkage is believed to be that it was impossible to remove the collar without destroying it and/or the shaft. Another analogous disadvantageous or undesirable feature is believed to be that the aforementioned heating of the thrust collar may have had a deleterious affect thereon, such as softening and/or distorting it. And yet another analogous disadvantageous or undesirable feature is believed to be that such heating of the thrust collar consumed energy which, at present, may be in short supply as illustrated by the energy conservation measures being promulgated by various concerned governmental agencies and utility companies.
Also in the past, thrust collars were pressed into displacement preventing engagement with the aforementioned conventional knurls about the shaft; however, at least one of the disadvantageous or undesirable features of this assembly scheme is believed to be that the press-fitting engagement of the thrust collar about the conventional knurls did not provide an oil tight seal between the thrust collar and the shaft when the thrust collar was also operating as a slinger or the like for lubricant employed in the prime mover.
Another one of the well known past arrangements utilized in positioning a thrust collar on the shaft of the rotatable assembly involved machining an annular groove in the shaft and providing a split ring retainer in the groove for positioning engagement with the thrust collar. Resilient means, such as a retaining spring or the like, may also have been provided so as to maintain the thrust collar in its mounted position about the shaft. At least one disadvantageous or undesirable feature of this type of arrangement is believed to be that the location of the thrust collar on the shaft was indefinite and could not be infinitely varied due to the accumulation of tolerances, i.e. tolerance buildup, between the various parts, such as the groove, the split ring retainer, the spring and the thrust collar itself, which not only deleteriously affected the thrust collar location but also the end play tolerances of the rotatable assembly with respect to the stationary assembly. Another disadvantageous or undesirable feature of this thrust collar arrangement is believed to be that the provision of the groove in the shaft served to weaken the shaft.